Do Merge two linked lists - C Data Structure

C examples for Data Structure:Linked List

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Description

Do Merge two linked lists

Demo Code

#include <stdio.h>
#include <stdlib.h>

typedef struct node {
    int num;/*from   ww w.jav a2  s.c  o  m*/
    struct node *next;
} Node, *NodePtr;

void printList(NodePtr);
NodePtr makeList(void);
NodePtr merge(NodePtr, NodePtr);

int main() {

    NodePtr A, B;

    printf("Enter numbers for the first list (0 to end)\n");

    A = makeList();

    printf("Enter numbers for the second list (0 to end)\n");

    B = makeList();

    printf("\nThe merged list is\n");

    printList(merge(A, B));
}

NodePtr makeList() {
    NodePtr makeNode(int), np, top = NULL, last;
    int n;

    if (scanf("%d", &n) != 1) 
       n = 0;
    while (n != 0) {
        np = makeNode(n);   //create a new node containing n
        if (top == NULL) 
           top = np;  //set top if first node
        else 
           last -> next = np; //set last -> next for other nodes
        last = np;  //update last to  new node
        if (scanf("%d", &n) != 1) 
           n = 0;
    }
    return top;
}

NodePtr makeNode(int n) {
    NodePtr np = (NodePtr) malloc(sizeof (Node));
    np -> num = n;
    np -> next = NULL;
    return np;
}

void printList(NodePtr np) {
    while (np != NULL) {  // as long as there's a node
        printf("%d ", np -> num);
        np = np -> next;  // go on to the next node
    }
    printf("\n\n");
}

NodePtr merge(NodePtr A, NodePtr B) {
    NodePtr C = NULL, last = NULL;
    if (A == NULL) 
       return B;
    if (B == NULL) 
       return A;
    
    //both lists are non-empty
    
    while (A != NULL && B != NULL) {
        if (A -> num < B -> num) {
            if (C == NULL) C = A; else last -> next = A;
            last = A;
            A = A -> next ;
        }
        else {
            if (C == NULL) C = B; else last -> next = B;
            last = B;
            B = B -> next ;
        }
    }
    
    if (A == NULL) 
       last -> next = B;
    else 
       last -> next = A;
    return C;
}

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